The present invention relates generally to microfabricated structures and methods for producing microfabricated structures. Merely by way of example, embodiments of the invention provide methods of fabricating integrated fluidic chips useful for performing a variety of biological and chemical analyses. The scope of the methods and systems described herein is also applicable to the fabrication and operation of fluidic devices used in regulating the flow of fluids.
Various approaches have been utilized to fabricate micro-fluidic pumps and valves. One method of producing micro-electromechanical (MEMS) structures that include pumps and valves is silicon-based bulk micro-machining. This is a subtractive fabrication method in which single crystal silicon is lithographically patterned and then etched to form three-dimensional structures. Another method of producing MEMS structures that include pumps and valves is surface micro-machining. This is an additive method in which layers of semiconductor-type materials such as polysilicon, silicon nitride, silicon dioxide, and various metals are sequentially added and patterned to make three-dimensional structures.
A limitation of the first approach of silicon-based micro-machining is that the stiffness of the semiconductor materials used in the process necessitates high actuation forces, which in turn result in large and complex designs. In fact, both bulk and surface micro-machining methods are limited by the stiffness of the materials used in the particular process. In addition, adhesion between various layers of the fabricated device presents problems for reliable operation. Another limitation of the first approach is that wafer bonding techniques are generally employed to create multilayer structures. A limitation of the second approach is that thermal stresses between the various layers of the device limits the total device thickness, often to approximately 20 μm. Using either of the above methods, clean room fabrication and careful quality control are typically required.
The present assignee has developed methods and systems for fabricating integrated (i.e., monolithic) fluidic chips including elastomeric structures based on a multilayer, soft lithography process. As described in U.S. Pat. No. 6,793,753, the disclosure of which is hereby incorporated by reference in its entirety for all purposes, multilayer elastomeric structures can be fabricated that include one or more layers that support fluid flow as well as one or more layers configured to control the flow of these fluids.
Despite the advances made in techniques related to the fabrication of such integrated fluidic chips, there is a need in the art for improved methods and systems for fabricating microfluidic devices.